In the documents filed for the “Mono-pendulum proximity switch” patent (Chinese patent application no. CN99249969.0, issued as Chinese patent no. CN2441223), the present applicant presented a mono-pendulum object detection method and device. It used an electromagnet to periodically attract an iron pendulum, causing it to move continually in the air as a single pendulum. In addition, it detects the movement status of the pendulum using an object-position signal-collecting component. When it swings, it emits a no-material signal. When the swinging stops, it emits a material-present signal. After many years of practical application, five deficiencies have been discovered: 1. During installation, it is necessary to ensure that the gap between the pendulum and the electromagnet is within the 6 mm to 12 mm range. If the gap is too small, then the amplitude of the pendulum's swing will be insufficient. If too large, the electromagnet cannot attract and hold the pendulum. Both of these instances have shown to adversely affect normal operation. 2. The swinging of the pendulum is driven by electromagnetic attractive force. The magnitude of the attractive force is inversely related to the square of the gap between the two. The only way to increase the maximum tolerated gap is to increase the ampere-turns and the cross-section area of the electromagnet. The consequences are a bulkier and heavier product, higher material consumption, higher power consumption, less than ideal attraction, difficulties in miniaturizing the product, high fabrication costs, as well as production and transportation challenges. 3. The high power consumption precludes the manufacture of a two-wire system, thus replacement with a two-wire system capacitance-type object-position switch is difficult. In addition, a single swing signal collection component is needed, resulting in a more complex structure. 4. The shared direction of the electromagnetic attractive force and the adhesive force facilitates adhesion, resulting in insufficient resistance to materials adhesion. 5. Poor resilience to high temperatures or high pressure. Other common object-position switches, such as rotary-resistance, tuning fork, capacitance, radio frequency admittance, and vibrating rod object-position switches, each have limitations. When a rotary-resistance switch has been operating for a long period of time, it becomes mechanically vulnerable to wear and corrosion breakdown, and may even ruin the electric motor, reducing service life. Tuning fork object-position switches tend to accumulate materials within the fork due to the adhesive effects of the materials and will cease vibrating, or long-term vibrations result in mechanical fatigue or breaking of the tuning fork; therefore reliability is low. In capacitance or radio frequency admittance object-position switches, the measurement electrodes tend to accumulate materials because of their adhesive effects. This gives rise to erroneous signals, and their sensitivity is greatly affected by temperature drift and time drift. Vibrating rod object-position switches require high voltage to begin vibrating and long resonance tubes. Their piezoelectric elements are easily affected by the environment and temperature and crack easily, and their sensitivity varies due to variations in the detected materials and therefore suffers from reliability issues. There is currently no ideal product for detecting objects under high-temperature, high-pressure, high-humidity, high-adhesion, and other harsh operating conditions.